Tai chi chuan focuses upon learning a sequence of movements. The movements are known as 'postures' and the sequence itself is called 'form'. The postures train good body usage and promote health.
In tai chi we look for optimal alignment and relaxation at all times. Form exists to provide a framework for movement.
The movement must ultimately be allowed to operate without the scaffolding of fixed postures.
Tai chi chuan is the movement itself, not the postures.